Refractive errors represent a broad category of vision problems where the eye does not properly focus light onto the retina, leading to blurry vision. When the shape of the eye or the cornea is slightly irregular, the light focuses incorrectly. Nearsightedness (myopia) and farsightedness (hyperopia) are the two most common types of these focusing issues affecting millions globally.
Understanding Nearsightedness and Farsightedness
Nearsightedness (myopia) occurs when light entering the eye focuses at a point in front of the retina, rather than directly on its surface. This misalignment typically happens because the eyeball has grown too long (axial elongation) or because the cornea is excessively curved. The result is that distant objects appear blurred, while objects close up can be seen clearly.
Farsightedness (hyperopia) is the opposite condition, where the light focuses at a point behind the retina. This typically results from an eyeball that is too short, or a cornea that lacks sufficient curvature. For a person with hyperopia, near objects are often blurry. Younger individuals can sometimes use eye muscles to compensate, but this often leads to eyestrain and headaches after prolonged close-up tasks.
Prevalence Data: Which Refractive Error is More Common?
Nearsightedness (myopia) is the more common and rapidly increasing refractive error worldwide. Global data indicate that myopia has reached levels that many experts now describe as an epidemic, particularly among children and young adults. Recent projections suggest that nearly half of the world’s population, approximately five billion people, will be myopic by the year 2050.
In certain regions, the prevalence is strikingly high, with countries in East Asia reporting that 80% to 90% of young adults are nearsighted. This upward trend in myopia is consistently observed across urban areas globally, significantly outpacing the occurrence of hyperopia. The consistent increase in myopic cases over the last few decades highlights a major shift in public health, making nearsightedness the dominant refractive error. Between 1990 and 2023, the pooled global prevalence of myopia among children and adolescents increased from 24.32% to 35.81%, with forecasts suggesting this figure will exceed 39% by 2050.
The Environmental and Genetic Drivers of Myopia
The surge in nearsightedness is understood to be the result of a complex interplay between genetic predisposition and environmental changes. Individuals with myopic parents are at a much higher risk of developing the condition, indicating a strong hereditary component. Researchers have identified over 400 genetic loci associated with refractive error, which help determine an individual’s susceptibility.
Genetics alone cannot explain the steep rise in prevalence over a short time, pointing to the power of environmental factors. The primary non-genetic drivers revolve around modern lifestyle changes, specifically the increase in “near work” activities. Prolonged periods of close-up focus, such as reading, studying, or using digital screens, place continuous strain on the eye’s focusing system.
The most influential environmental factor is the insufficient time spent outdoors, particularly during childhood. Exposure to natural outdoor light is believed to stimulate the release of dopamine in the retina, which plays a role in regulating the eye’s growth and preventing axial elongation. Studies suggest that children who spend less time outside have a higher risk of developing myopia.
Treatment Options for Refractive Errors
For both nearsightedness and farsightedness, the most common treatment involves the use of corrective lenses. Eyeglasses and contact lenses work by bending light rays before they enter the eye, ensuring they focus directly onto the retina. These devices provide clear vision and are the standard initial recommendation for managing refractive errors.
Permanent correction can be achieved through refractive surgeries like LASIK and PRK, which use a laser to reshape the cornea and alter its focusing power. These procedures are effective for correcting stable prescriptions in adults. For children with progressive myopia, the focus shifts to slowing the eye’s axial elongation to prevent high levels of nearsightedness.
Newer treatments known as myopia control methods are now common practice for managing progression. These methods focus on slowing the eye’s growth and include:
- Low-dose atropine eye drops, administered nightly to help slow the growth of the eye.
- Orthokeratology (Ortho-K) lenses, worn overnight to temporarily reshape the cornea.
- Multifocal soft contact lenses, designed to slow progression during daytime wear.